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SubjectRe: [PATCH v2 08/18] x86/dumpstack: Handle stack overflow on all stacks
On Tue, Nov 21, 2017 at 08:44:03PM -0800, Andy Lutomirski wrote:
> We currently special-case stack overflow on the task stack. We're
> going to start putting special stacks in the fixmap with a custom
> layout, so they'll have guard pages, too. Teach the unwinder to be
> able to unwind an overflow of any of the stacks.
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/kernel/dumpstack.c | 26 ++++++++++++++++----------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index 5e7d10e8ca25..635dcbfe2398 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -90,24 +90,30 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
> * - task stack
> * - interrupt stack
> * - HW exception stacks (double fault, nmi, debug, mce)
> + * - SYSENTER stack
> *
> - * x86-32 can have up to three stacks:
> + * x86-32 can have up to four stacks:
> * - task stack
> * - softirq stack
> * - hardirq stack
> + * - SYSENTER stack
> */
> for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
> const char *stack_name;
>
> - /*
> - * If we overflowed the task stack into a guard page, jump back
> - * to the bottom of the usable stack.
> - */
> - if (task_stack_page(task) - (void *)stack < PAGE_SIZE)
> - stack = task_stack_page(task);
> -
> - if (get_stack_info(stack, task, &stack_info, &visit_mask))
> - break;
> + if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
> + /*
> + * We weren't on a valid stack. It's possible that
> + * we overflowed a valid stack into a guard page.
> + * See if the next page up is valid to that we can

s/to/so/

> + * generate some kind of backtrace if this happens.
> + */
> + stack = (unsigned long *)
> + PAGE_ALIGN((unsigned long)stack);
> + if (get_stack_info(stack, task, &stack_info,
> + &visit_mask))

Yeah, let them stick out.

With that:

Reviewed-by: Borislav Petkov <bp@suse.de>

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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